#include<bits/stdc++.h>

using namespace std;

int main() {
	int a[]={1,2,4,4,6,10,123,125,200};
	int n=sizeof(a)/sizeof(a[0]);
	int key=17;	
	int flag=0;
	for(int i=0;i<n;i++){
		if(a[i]==key){
			cout<<i<<endl;
			flag=1;
			break;
		}
	}
	if(flag==0)
		cout<<-1<<endl;
	return 0;
}
